It is known to use RFID “Radio Frequency Identification” transponders—often also referred to as RFID tags or radio tags—e.g. in the field of logistics for identifying products and assemblies of products.
RFID tags enable automatic identification and locating of objects and facilitate therewith significantly the registering and providing of information and data. An RFID system is composed of an RFID transponder, or an RFID tag, which is associated with an object and includes the more relevant information and data, and a reading device for read-out of the information and data. Coupling between RFID tag and reading device occurs via short range, magnetic, alternating fields or high frequency radio waves of greater range produced by the reading device. Data transmission occurs via the alternating fields or the high frequency radio waves produced by the reading devices. In many cases, the chip is also supplied with energy via the alternating fields or the high frequency radio waves.
RFID transponders/RFID tags include an RFID chip and an RFID antenna and differ as a function of transmission frequency, manufacturer and purpose of use. The RFID chip is usually composed of an analog circuit for receiving and sending data, a digital circuit and a memory, which usually can be over-written multiple times. The digital circuit is often implemented via a microcontroller. In the case of a passive RFID chip, the energy received during communication via the antenna serves for the energy supply of the microcontroller. In the case of active RFID tags, the energy supply of the microcontroller occurs via its own installed energy source, e.g. a single-use battery. In the case of half active RFID tags, the installed energy source supplies only the digital circuit, e.g. the microcontroller.
RFID tags work, depending on type, in the long wave region at 125-134 kHz, the short wave region at 13.56 MHz. the UHF region at 865-869 MHz. or 950 MHz or the SHF region at 2.45 GHz and 5.8 GHz.
The activated microcontroller in the RFID tag decodes commands sent by the reading device. The reading device codes the response and modulates it into the radiated electromagnetic field by field weakening in contact free, short circuit (load modulation) or in opposite phase reflection of the alternating field sent by the reading device (modulated back scattering). The RFID tag transmits, for example, its own unchangeable serial number, the information and data of the associated object, etc. The RFID tag thus itself produces no field; rather, it influences the electromagnetic transmission field of the reading device.
In the case of field devices of automation technology with metal housing, the metal housing material effects a shielding of the electromagnetic data- and/or energy transmission, whereby the transmission path is usually limited to a few centimeters and therewith to the close proximity of the field device. The use of RFID technology in the field of automation technology is limited to a few special cases. A general use, or retrofitting, of field devices with RFID technology is, so far, not possible.